22,723 research outputs found
Feshbach spectroscopy of an ultracold Rb-Cs mixture
No full textThis thesis reports the observation of interspecies Feshbach resonances in an ultracold mixture of Rb and Cs atoms. A versatile combined magnetic and optical potential has been designed and constructed which is capable of bringing both and to degeneracy, and reaching high phase-space density in . High phase-space density mixtures are the first step required in the production of ultracold polar molecules, the topic of much current research.
The apparatus capitalises on the efficient capture of atoms by a magnetic trap from a magneto-optical trap, and the efficient sympathetic cooling of Cs by Rb therein. Upon transfer to the crossed optical dipole trap condensates in excess of atoms and approximately atoms are produced after direct evaporation and gravito-magnetic tilting of the potential. The observation of six interspecies - Feshbach resonances are reported, three of which had only been predicted theoretically, allowing testing and development of the theoretical model. Furthermore, the extrapolation of this model has predicted numerous Feshbach resonances between and , none of which have been experimentally observed prior to this work. The versatile nature of this apparatus is discussed, including the application of the current system to cooling of . Initial experiments observed seven interspecies resonances, including a broad s-wave resonance at a magnetic field of G which is in excellent agreement with the theoretical prediction. Further work has revealed that fourteen Feshbach resonances exist in the 0-700 G magnetic field range between and atoms in the and states, respectively. Several of these resonances would be ideal for magneto-association of RbCs molecules, prior to transfer to the rovibrational ground-state
CS Track Investigating Citizen Science brochure
No full textCS Track, a research project funded by the European Commission, aims at broadening knowledge about citizen science by applying data analysis to publicly available information from the web and collecting complementary data through questionnaires and interviews with people who take part in CS activities. For this purpose, CS Track has collected publicly available data on more than 4500 projects from websites and online platforms and conducted
a survey with more than 1000 participants from 30 European countries. Taking this approach, CS Track generated insights about citizen science and its impact in various areas during the past three years.
“Citizen science offers great potential for science and society, but this potential can only be fully realized if certain conditions are met. These conditions for success include, among others, strategies to ensure the active and long-term cooperation of citizen scientists. The aim must be to create an environment that motivates participants to get involved in the respective project - for example through educational offers, regular communication between volunteers and professional scientists in both directions, events, awards, certification and so forth. This aspect in particular is often very time-consuming and cost-intensive for
the project initiators, but can be the deciding factor as to whether a project succeeds or fails.” Dr Raul Drachman, CS Track project coordinator.
This brochure provides a summary of the research work carried out by the project team in the first 30 months of CS Track’s lifetime
VIBRATIONAL PREDISSOCIATION STUDIES OF AND SOLVATED ION CLUSTERS
No full textAuthor Institution: School of Chemical Sciences, University of IllinoisVibrational predissoclation spectra of masa-selected and solvated ion clusters have been observed by exciting the CO stretching mode of the solvent molecules in the range. The solvated ions are produced by combining a thermlontc Cs ion source and supersonic nozzle. From the spectral dependence on the solvent number surrounding the Cs ion, we have observed the formation of solvation shells. Ten MeOH or six EtOH molecules are required to complete the first solvation shell around the Cs ion in the gas phase. The relationship between neutral methanol and ethanol clusters and the solvated cesium ions will be discussed
PiLa-CS Professional Learning Community - Workshop 2 Resources
No full textDuring the Summer of 2021 and 2022, the Participating in Literacies and Computer Science (PiLa-CS) Research Practice Partnership convened and supported a community of practice to learn more about how to enable better CS teaching for emergent bilinguals. These are materials from Workshop 2 of the PLC.Sponsored by the National Science Foundation under NSF grant CNS-1738645 and DRL-1837446. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation
Long-Range Binding of Defect Clusters Leads to Suppressed Ion Mobility in Cs-Doped Methylammonium Lead Iodide
No full textPartial substitution of CH3NH3+ with Cs+ ions has been reported to suppress the
iodide
vacancy diffusion in methylammonium lead iodide (MAPI) and enhance
its structural stability. However, the defect chemistry of partial
cation-substituted MAPI, i.e., Csx(CH3NH3)1–xPbI3, and the effect of stoichiometry on the halide ion mobility
have not been systematically investigated in the literature. Herein,
classical force field-based atomistic simulations were performed to
calculate the defect cluster binding energies and halide ion migration
barriers in Csx(CH3NH3)1–xPbI3 for different
Cs-doping concentrations, exhibiting a weak dependence on stoichiometry.
Higher diffusion activation energy due to Cs doping results mainly
from the long-range binding between I– vacancy clusters
and Cs+, which reduces the concentration of mobile vacancies.
Clusters of Cs+ with up to 3 I– vacancies
were found to be energetically stable with a binding energy of ∼0.2
eV at 6 Å from the Cs+ defect center. Tilting and
rotation of neighboring PbI6 octahedra were also observed
in doped MAPI, which causes a nonlocal strain in the crystal. Experimental
characterization of Cs-doped MAPI solar cells confirmed the reduced
hysteresis and its weaker dependence on Cs concentration along with
higher activation energy of halide migration in Cs-doped MAPI. Time-resolved
photoluminescence and thermal admittance spectroscopy tests also showed
reduced defect density in the Cs-doped perovskite because of suppressed
halide migration that leads to lower loss of halides. Weaker dependence
of diffusion activation energy on the dopant concentration opens up
the possibility for multication doping to further maximize the strain
effect
Translanguaging Pedagogy in CS Ed
No full textEpisode 3: Translanguaging pedagogy in CS Education
This video looks at how multilingual students already use translanguaging in their computer science classes and discusses how CS educators can further support them with translanguaging pedagogy, a framework that prompts teachers to consider their stance, design, and shifts.
Featuring team members from Participating in Literacies and Computer Science (PiLa-CS), https://www.pila-cs.orgEpisode 3: Translanguaging pedagogy in CS Education
This video looks at how multilingual students already use translanguaging in their computer science classes and discusses how CS educators can further support them with translanguaging pedagogy, a framework that prompts teachers to consider their stance, design, and shifts.
Featuring team members from Participating in Literacies and Computer Science (PiLa-CS), https://www.pila-cs.orgSponsored by the National Science Foundation under NSF grant CNS-1738645 and DRL-1837446. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation
PiLa-CS Professional Learning Community - Design Journal Template
No full textDuring the Summer of 2021 and 2022, the Participating in Literacies and Computer Science (PiLa-CS) Research Practice Partnership convened and supported a community of practice to learn more about how to enable better CS teaching for emergent bilinguals. These are materials from from the PLC for a Design Journal to act as a planing template for teachers.Sponsored by the National Science Foundation under NSF grant CNS-1738645 and DRL-1837446. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation
Long-term behaviour of Cs-137, Cs-133 and K in beech trees of French forests
No full textInternational audienceIn the long-term after atmospheric deposit onto a forest ecosystem, Cs-137 becomes incorporated into the biogeochemical cycle of stable elements and progressively reaches a quasi-equilibrium state. This study aimed at determining to what extent Cs-137 activity distribution in tree vegetation could be predicted from that of stablecaesium (Cs-133) and potassium (K), which are known to be stable chemical analogues and competitors for Cs-137 intake in tree organs. Field campaigns that focused on beech trees (Fagus sylvatica L.) were conducted in 2021 in three French forest stands with contrasted characteristics regarding either the contribution of global vs. Chornobyl fallouts, soil or climatic conditions. Decades after Cs-137 fallouts, it was found that more than 80% of the total radioactive inventory in the system remained confined in the top 20 cm mineral layers, while organic layers and beech vegetation (including roots) contributed each to less than 1.5%. The enhanced downward migration of Cs-137 in cambisol than podzol forest sites was presumably due to migration of clay particles andbioturbation. The distribution of Cs-137 and Cs-133 inventories in beech trees was very similar among sites but differed from that of K due a higher accumulation of Cs isotopes in roots (40–50% vs. <25% for K). The aggregated transfer factor (Tag) of Cs-137 calculated for aerial beech organs were all lower than those reported in literature more than 20 years ago, this suggesting a decrease of bioavailability in soil due to ageing processes. Regarding their variability, Tags were generally lower by a factor 5 at the cambisol site, which was fairly well explained by a much higher value of RIP (radiocesium immobilisation potential). Cs-137 concentrations in trees organs normalized by the soil exchangeable fractions were linearly correlated to those of Cs-133 and the best fit was found for the linear regression model without intercept indicating that no more contribution of the foliar uptake could be observed on long term. Provided that the vertical distribution of caesium concentrations and fineroot density are properly measured or estimated, Cs-133 was shown to be a much better proxy than K to estimate the root transfer of Cs-137
Modeling and interpreting element ratios in water and sediments: A sensitivity analysis of post-Chernobyl Ru : Cs ratios.
No full textWhen elements are simultaneously added to lakes, experimentally or by accident, their ratios in the water phase and in bottom sediments can change with time due to differential partitioning between solution and suspended particles or sediments. A number of equations are developed to show the change of ratio with time in water and sediments assuming simultaneous pulse inputs followed by a range of combinations of loss processes from solution (i.e. hydraulic losses, sorption to particles followed by settling, and diffusion into the sediments). The pattern of events is discussed both for pulse events with specific limiting assumptions and for combined continuous and pulse inputs. The models show that elemental ratios in sediments are generally less sensitive indicators of differential partitioning than are elemental ratios in water. For lakes with long residence times, the long-term elemental ratio in the sediments does not differ from that in the initial spike to the water column, but for short residence times, it is directly dependent on the ratio of either partition or diffusion coefficients. The models are used to interpret Ru : Cs ratios measured in the water and sediments of Esthwaite Water subsequent to the pulse input of Chernobyl fallout. The ratios can be explained by assuming nuclides were lost either by flushing and sorption or by flushing, sorption, and diffusion. The process combination of flushing and diffusion is incompatible with the observed constant ratios
Long-interval facilitation and inhibition are differentially affected by conditioning stimulus intensity over different time courses
No full textIntracortical facilitatory and inhibitory processes in the primary motor cortex (M1) play an important role in both the preparation and execution of motor tasks. Here we aimed to (1) confirm the existence of, and further characterise, intracortical facilitation at long conditioning-test stimulus intervals at subthreshold conditioning stimulus (CS) intensities and (2) identify the threshold for long-interval intracortical inhibition (LICI) at different inter-stimulus intervals (ISIs). To examine facilitation, stimulus-response curves at ISIs of 100 and 150ms were obtained using a range of subthreshold CS intensities. LICI stimulus-response curves were also obtained using varying CS intensities at ISIs of 100 (LICI100) and 150ms (LICI150). Facilitation of the conditioned MEP was observed at subthreshold CS intensities at an ISI of 100ms. LICI100 was observed at a lower CS intensity than LICI150. First, we provide evidence of a long-interval facilitation and provide some evidence consistent with a cortical origin of this facilitation. Second, the lower threshold for evoking LICI100 than LICI150 suggests an intensity-duration effect whereby a more intense CS results in longer duration LICI. Investigation of the interaction between LICI and long-interval facilitation might help to elucidate the functional importance of these processes. © 2014
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